Alpha Librae

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α Librae
Location of α Librae (circled)
Characteristics
α1 Lib
Spectral type F3 V[1] + M0–1 V[2]
U−B color index −0.02[3]
B−V color index +0.39[3]
α2 Lib
Evolutionary stage Main sequence[4][5] or blue straggler (α2 A)[6]
Spectral type kA2hA5mA4 IV-V[7]
U−B color index +0.10[3]
B−V color index +0.15[3]
Astrometry
α1 Lib
Radial velocity (Rv)−23.8±0.3[8] km/s
Proper motion (μ) RA: −136.27[9] mas/yr
Dec.: −59.04[9] mas/yr
Parallax (π)43.52±0.43 mas[9]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)+3.35[10]
α2 Lib
Proper motion (μ) RA: −105.68[9] mas/yr
Dec.: −68.40[9] mas/yr
Parallax (π)43.03±0.19 mas[9]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)+0.88[11]
Orbit[12]
Primaryα1 Lib A
Nameα1 Lib B
Period (P)16.229±0.043 yr
Semi-major axis (a)0.346±0.006″
Eccentricity (e)0.244±0.008
Inclination (i)54.4±1.5°
Longitude of the node (Ω)122.7±1.4°
Periastron epoch (T)2021.95±0.12
Argument of periastron (ω)
(secondary)		184.1±3.3°
Semi-amplitude (K1)
(primary)		3.83±0.12 km/s
Orbit[8]
Primaryα2 Lib A
Nameα2 Lib B
Period (P)70.34±0.07 days
Semi-major axis (a)0.52[6] au
Eccentricity (e)0.41±0.02
Inclination (i)71±3[6]°
Longitude of the node (Ω)333±17[6]°
Periastron epoch (T)JD 2455294.3±0.5
Argument of periastron (ω)
(secondary)		48±7°
Semi-amplitude (K2)
(secondary)		43.1±0.5 km/s
Details
α2 Lib A
Mass1.95[6] M☉
Radius2.21[6] R☉
Surface gravity (log g)3.91[7] cgs
Temperature8,200[6] K
Age700[6] Myr
α2 Lib B
Mass1.79[6] M☉
Radius1.92[6] R☉
Temperature7,930[6] K
Age700[6] Myr
α1 Lib A
Mass1.36±0.02[13] M☉
Radius1.50[14] R☉
Luminosity3.83[13] L☉
Surface gravity (log g)4.23[13] cgs
Temperature6,707±56[13] K
Metallicity [Fe/H]−0.03[13] dex
Rotational velocity (v sin i)5.95[13] km/s
Age1.01±0.24[13] Gyr
α1 Lib B
Mass0.5–0.6[2] M☉
Other designations
Template:Odlist
α Lib B: Template:Odlist[15]
α Lib A: Template:Odlist[16]
Database references
SIMBADα1 Lib
α2 Lib

Alpha Librae (α Librae, abbreviated Alpha Lib, α Lib) is a quadruple star system and, despite its 'alpha' designation, it is the second-brightest star in the constellation of Libra. The two components are designated α1 Librae and α2 Librae. The system bore the traditional name of Zubenelgenubi /zuːˌbɛnɛldʒɪˈnuːbi/,[17] though the International Astronomical Union now regards that name as only applying to α2 Librae.[18]

Alpha2 Librae is 0.33 degrees north of the ecliptic so it can be occulted by the Moon and (very rarely) by planets. It was occulted by Venus on October 25, 1947;[19] the next occultation by a planet will be by Mercury on 10 November 2052.[20] Both components are eclipsed (occulted) by the sun from about 7–9 November.[21] Thus the star can be viewed the whole night, crossing the sky, in early May.

Nomenclature

α Librae (Latinised to Alpha Librae) is the system's Bayer designation.

Zubenelgenubi /ˌzuːbənɛldʒəˈnuːbi/, also rendered Zuben Elgenubi, derives from the Arabic ّالزُبَانَى الجَنُوبِي al-zubānā al-janūbiyy "the southern claw", which was coined before Libra was recognized as a constellation distinct from Scorpius. The alternative name Kiffa Australis (Elkhiffa Australis) is a partial Latin translation of the Arabic al-kiffah al-janubiyyah الكفة الجنوبية "southern pan [of the scales]". Another name used in older astronomy texts, equivalent to "southern pan", was Lanx Australis.[22]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[23] to catalogue and standardize proper names for stars. The WGSN approved the name Zubenelgenubi for α2 Librae on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.[18]

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Root, refers to an asterism consisting of α2 Librae, ι Librae, γ Librae and β Librae.[24] Consequently, the Chinese name for α2 Librae itself is Script error: No such module "Lang". (Script error: No such module "Lang".), "the First Star of Root".[25]

Properties

Aa
α2 Lib (70.3 days)
Ab
231″ separation
Ba
α1 Lib (16.3 years)
Bb

Hierarchy of orbits in the α Librae system

Alpha Librae is about 77 light-years (24 parsecs) from the Sun. The two brightest components of Alpha Librae form a double star moving together through space as common proper motion companions. They are separated in the sky by an angular distance of 231" (3'51"). The position angle of the companion is 314 degrees. The brighter of the two is a white star of spectral type A3, with an apparent magnitude of 2.8. Its companion is a type F4 star of apparent brightness 5.2. They are probably members of the Castor Moving Group of stars that have a similar motion through space and share a common origin some 200 million years ago.[2]

Alpha2 Librae

The brightest member, α2 Librae or α Librae A, is itself a spectroscopic binary system. The components have similar masses (mass ratio of 0.92) but the primary has a rotational velocity three times higher than its companion, which could be caused by them having significantly misaligned spin axes or if the primary is a merger product.[6]

Alpha1 Librae

The second member, α1 Librae or α Librae B, is separated from the primary system by around 5,360 AU.[6] It too is a spectroscopic binary with an orbital period of 5,870 days and an angular separation of 0.383 arcseconds;[12] equal to about 9 au.[6]

KU Librae

The system may have a fifth component, the star KU Librae at a separation of 2.6°, thus forming a hierarchical quintuple star system. KU Lib shares a similar motion through space to the Alpha Librae system, but is separated from the other stars by about a parsec. It is sufficiently close to be gravitationally bound to the other members,[2] but has a substantially different metallicity, making it unlikely to be physically bound to the system.[26]

See also

References

  1. ^ Page Module:Citation/CS1/styles.css has no content.Houk, N.; Smith-Moore, M. (1988). "Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4, Declinations -26°.0 to -12°.0". Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4. Bibcode:1988mcts.book.....H.
  2. ^ a b c d Page Module:Citation/CS1/styles.css has no content.Caballero, J. A. (May 2010). "Reaching the boundary between stellar kinematic groups and very wide binaries. II. α Librae + KU Librae: a common proper motion system in Castor separated by 1.0 pc". Astronomy and Astrophysics. 514: A98. arXiv:1001.5432. Bibcode:2010A&A...514A..98C. doi:10.1051/0004-6361/200913986. S2CID 118875432.
  3. ^ a b c d Page Module:Citation/CS1/styles.css has no content.Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  4. ^ Page Module:Citation/CS1/styles.css has no content.Zorec, J.; Royer, F. (January 2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy and Astrophysics. 537: A120. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691. ISSN 0004-6361.
  5. ^ Page Module:Citation/CS1/styles.css has no content.Takeda, Yoichi; Kawanomoto, Satoshi; Ohishi, Naoko; Kang, Dong-Il; Lee, Byeong-Cheol; Kim, Kang-Min; Han, Inwoo (October 2018). "Photospheric carbon, nitrogen, and oxygen abundances of A-type main-sequence stars". Publications of the Astronomical Society of Japan. 70 (5): 91. arXiv:1807.06265. Bibcode:2018PASJ...70...91T. doi:10.1093/pasj/psy091. ISSN 0004-6264.
  6. ^ a b c d e f g h i j k l m n o Page Module:Citation/CS1/styles.css has no content.Waisberg, Idel; Klein, Ygal; Katz, Boaz (2023-08-23). "Hidden Companions to Intermediate-mass Stars. X. Solving for the Mass Ratio in the Spectroscopic Binary Zubenelgenubi = α 2 Librae*". Research Notes of the AAS. 7 (8): 180. Bibcode:2023RNAAS...7..180W. doi:10.3847/2515-5172/acf28f. ISSN 2515-5172.
  7. ^ a b Page Module:Citation/CS1/styles.css has no content.Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID 119476992.
  8. ^ a b Page Module:Citation/CS1/styles.css has no content.Fuhrmann, K.; Chini, R.; Barr, A.; Buda, L.-S.; Kaderhandt, L.; Pozo, F.; Ramolla, M. (2014). "On the bright A-type star Alpha Librae A". Monthly Notices of the Royal Astronomical Society. 437 (3): 2303. Bibcode:2014MNRAS.437.2303F. doi:10.1093/mnras/stt2046.
  9. ^ a b c d e f Page Module:Citation/CS1/styles.css has no content.van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  10. ^ Page Module:Citation/CS1/styles.css has no content.Holmberg, J.; Nordström, B.; Andersen, J. (July 2009). "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics". Astronomy and Astrophysics. 501 (3): 941–947. arXiv:0811.3982. Bibcode:2009A&A...501..941H. doi:10.1051/0004-6361/200811191. S2CID 118577511.
  11. ^ Page Module:Citation/CS1/styles.css has no content.Allende Prieto, C.; Lambert, D. L. (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: Masses, radii and effective temperatures". Astronomy and Astrophysics. 352: 555. arXiv:astro-ph/9911002. Bibcode:1999A&A...352..555A.
  12. ^ a b Page Module:Citation/CS1/styles.css has no content.Tokovinin, Andrei; Mason, Brian D.; Mendez, Rene A.; Costa, Edgardo (2024). "Speckle Interferometry at SOAR Telescope in 2023". The Astronomical Journal. 168 (1): 28. Bibcode:2024AJ....168...28T. doi:10.3847/1538-3881/ad4d56.
  13. ^ a b c d e f g Page Module:Citation/CS1/styles.css has no content.Luck, R. Earle (2018-03-01). "Abundances in the Local Region. III. Southern F, G, and K Dwarfs". The Astronomical Journal. 155 (3): 111. Bibcode:2018AJ....155..111L. doi:10.3847/1538-3881/aaa9b5. ISSN 0004-6256. Alpha1 Librae's database entry at VizieR.
  14. ^ Page Module:Citation/CS1/styles.css has no content.Stassun, Keivan G.; et al. (2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467.
  15. ^ Page Module:Citation/CS1/styles.css has no content."* alf01 Lib". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2007-01-23. {{cite web}}: Invalid |mode=Script error: No such module "Citation mode". (help)
  16. ^ Page Module:Citation/CS1/styles.css has no content."* alf02 Lib". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2007-01-23. {{cite web}}: Invalid |mode=Script error: No such module "Citation mode". (help)
  17. ^ Page Module:Citation/CS1/styles.css has no content.Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  18. ^ a b Page Module:Citation/CS1/styles.css has no content."IAU Catalog of Star Names". Retrieved 28 July 2016.
  19. ^ Page Module:Citation/CS1/styles.css has no content.Können, G. P.; Van Maanen, J. (April 1981). "Planetary occultations of bright stars". Journal of the British Astronomical Association. 91: 148–157. Bibcode:1981JBAA...91..148K.
  20. ^ Peuschel, Marco (2003). "Astronomische Ereignisse der besonderen Art" Script error: No such module "webarchive".. Retrieved July 10, 2005.
  21. ^ In the Sky Earth astronomy reference utility showing the ecliptic and relevant date as at J2000 - present
  22. ^ Philippe La Hire, "Tabulae Astronomicae" (1727), see star table, page 13.
  23. ^ Page Module:Citation/CS1/styles.css has no content."IAU Working Group on Star Names (WGSN)". International Astronomical Union. Retrieved 22 May 2016.
  24. ^ Template:In lang 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, Template:ISBN.
  25. ^ Template:In lang 香港太空館 - 研究資源 - 亮星中英對照表 Script error: No such module "webarchive"., Hong Kong Space Museum. Accessed on line November 23, 2010.
  26. ^ Page Module:Citation/CS1/styles.css has no content.Fuhrmann, K.; Chini, R. (2015). "Multiplicity among F-type stars. II". The Astrophysical Journal. 809 (1): 107. Bibcode:2015ApJ...809..107F. doi:10.1088/0004-637X/809/1/107. S2CID 126218052.

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